Black Hills (BKH) 10-Q 5 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-31303
Entity Registrant Name	Black Hills Corporation
Entity Incorporation, State or Country Code	SD
Entity Tax Identification Number	46-0458824
Entity Address, Address Line One	7001 Mount Rushmore Road
Entity Address, City or Town	Rapid City
Entity Address, State or Province	SD
Entity Address, Postal Zip Code	57702
City Area Code	605
Local Phone Number	721-1700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common stock of $1.00 par value
Trading Symbol	BKH
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		62,749,727
Entity Central Index Key	0001130464
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--03-31

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenues	$ 537,050	$ 597,810
Operating expenses:
Fuel, purchased power and cost of natural gas sold	187,879	249,742
Operations and maintenance	125,466	123,584
Depreciation, depletion and amortization	56,402	51,028
Taxes - property and production	14,118	13,325
Total operating expenses	383,865	437,679
Operating income	153,185	160,131
Other income (expense):
Interest expense incurred net of amounts capitalized (including amortization of debt issuance costs, premiums and discounts)	(35,781)	(35,016)
Interest income	328	299
Impairment of investment	(6,859)	0
Other income (expense), net	2,353	(789)
Total other income (expense)	(39,959)	(35,506)
Income before income taxes	113,226	124,625
Income tax (expense)	(16,002)	(17,263)
Net income	97,224	107,362
Net income attributable to noncontrolling interest	(4,050)	(3,554)
Net income available for common stock	$ 93,174	$ 103,808
Earnings per share of common stock:
Earnings (loss) per share, Basic (usd per share)	$ 1.51	$ 1.73
Earnings (loss) per share, Diluted (usd per share)	$ 1.51	$ 1.73
Weighted Average Number of Shares Outstanding, Basic and Diluted [Abstract]
Basic (in shares)	61,778	59,920
Diluted (in shares)	61,856	60,060

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net income	$ 97,224	$ 107,362
Other comprehensive income (loss), net of tax:
Benefit plan liability adjustments - net gain (net of tax of $(17) and $0, respectively	55	0
Reclassification adjustments of benefit plan liability - prior service cost (net of tax of $7 and $5, respectively)	(23)	(14)
Reclassification adjustments of benefit plan liability - net gain (net of tax of $(95) and $(53), respectively)	502	167
Other comprehensive income, net of tax	1,273	457
Comprehensive income	98,497	107,819
Net Income (Loss) Attributable to Noncontrolling Interest	4,050	3,554
Comprehensive income available for common stock	94,447	104,265
Interest rate swaps
Other comprehensive income (loss), net of tax:
Reclassification of net realized (gains) losses	543	550
Commodity Contract
Other comprehensive income (loss), net of tax:
Reclassification of net realized (gains) losses	371	(426)
Net unrealized gains (losses) on commodity derivatives (net of tax of $54 and $(54), respectively)	$ (175)	$ 180

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Benefit plan liability adjustments - net gain (loss) (tax) benefit	$ (17)	$ 0
Reclassification adjustment of benefit plan liability - prior service costs, tax	7	5
Reclassification adjustment of benefit plan liabilities - net gain (loss), (tax) benefit	(95)	(53)
Interest rate swaps
Reclassification of net realized gains/losses, (tax) benefit	(170)	(163)
Commodity Contract
Net unrealized gains/losses on commodity derivatives, (tax) benefit	54	(54)
Reclassification of net realized gains/losses, (tax) benefit	$ (115)	$ 128

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 54,137	$ 9,777
Restricted cash and equivalents	4,027	3,881
Accounts receivable, net	238,903	255,805
Materials, supplies and fuel	92,894	117,172
Derivative assets, current	1,780	342
Income tax receivable, net	22,319	16,446
Regulatory assets, current	49,415	43,282
Other current assets	26,198	26,479
Total current assets	489,673	473,184
Investments	15,250	21,929
Property, plant and equipment	6,808,261	6,784,679
Less: accumulated depreciation and depletion	(1,223,979)	(1,281,493)
Total property, plant and equipment, net	5,584,282	5,503,186
Other assets:
Goodwill	1,299,454	1,299,454
Intangible assets, net	13,083	13,266
Regulatory assets, non-current	222,814	228,062
Other assets, non-current	24,258	19,376
Total other assets, non-current	1,559,609	1,560,158
TOTAL ASSETS	7,648,814	7,558,457
Current liabilities:
Accounts payable	136,344	193,523
Accrued liabilities	203,445	226,767
Derivative liabilities, current	852	2,254
Regulatory liabilities, current	54,345	33,507
Notes payable	319,125	349,500
Current maturities of long-term debt	5,743	5,743
Total current liabilities	719,854	811,294
Long-term debt, net of current maturities	3,136,887	3,140,096
Deferred credits and other liabilities:
Deferred Income Tax Liabilities, Net	387,939	360,719
Regulatory liabilities, non-current	504,149	503,145
Benefit plan liabilities	152,693	154,472
Other deferred credits and other liabilities	122,869	124,662
Total deferred credits and other liabilities	1,167,650	1,142,998
Commitments and contingencies (See Notes 7, 9, 12, 13)
Equity:
Common stock $1 par value; 100,000,000 shares authorized; issued 62,772,978 and 61,480,658 shares, respectively	62,773	61,481
Additional paid-in capital	1,652,861	1,552,788
Retained earnings	838,841	778,776
Treasury stock, at cost – 24,656 and 3,956 shares, respectively	(1,925)	(267)
Accumulated other comprehensive income (loss)	(29,382)	(30,655)
Total stockholders’ equity	2,523,168	2,362,123
Noncontrolling interest	101,255	101,946
Total equity	2,624,423	2,464,069
TOTAL LIABILITIES AND TOTAL EQUITY	$ 7,648,814	$ 7,558,457

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common Stock, Par Value (usd per share)	$ 1	$ 1
Common Stock Issued (in shares)	62,772,978	61,480,658
Treasury Stock (in shares)	24,656	3,956
Common Stock Authorized (in shares)	100,000,000	100,000,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net income	$ 97,224	$ 107,362
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	56,402	51,028
Deferred financing cost amortization	2,237	2,007
Impairment of investment	6,859	0
Stock compensation	291	3,296
Deferred income taxes	21,876	19,602
Employee benefit plans	1,235	3,137
Other adjustments, net	892	4,428
Changes in certain operating assets and liabilities:
Materials, supplies and fuel	19,222	29,387
Accounts receivable and other current assets	8,171	(15,857)
Accounts payable and other current liabilities	(43,297)	(41,689)
Regulatory assets - current	20,679	13,031
Regulatory liabilities - current	1,316	(1,635)
Other operating activities, net	(1,138)	1,796
Net cash provided by operating activities	191,969	175,893
Investing activities:
Property, plant and equipment additions	(171,882)	(144,126)
Other investing activities	(1,202)	(901)
Net cash (used in) investing activities	(173,084)	(145,027)
Financing activities:
Dividends paid on common stock	(32,902)	(30,332)
Common stock issued	99,321	19,949
Net (payments) borrowings of short-term debt	(30,375)	(20,970)
Long-term debt - repayments	(4,291)	(1,436)
Distributions to noncontrolling interest	(4,741)	(4,846)
Other financing activities	(1,391)	(1,657)
Net cash provided by (used in) financing activities	25,621	(39,292)
Net change in cash, restricted cash and cash equivalents	44,506	(8,426)
Cash, restricted cash and cash equivalents at beginning of period	13,658	24,145
Cash, restricted cash and cash equivalents at end of period	58,164	15,719
Supplemental Cash Flow Information [Abstract]
Interest (net of amounts capitalized)	(21,776)	(30,672)
Income taxes	0	8
Accrued property, plant and equipment purchases at March 31	$ 53,011	$ 56,571

Condensed Consolidated Statem_5

Condensed Consolidated Statements Of Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (loss)	Noncontrolling Interest
Common Stock, Shares, Outstanding at Dec. 31, 2018		60,048,567	44,253
Total equity at Dec. 31, 2018	$ 2,287,423	$ 60,049	$ (2,510)	$ 1,450,569	$ 700,396	$ (26,916)	$ 105,835
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	107,362				103,808		3,554
Other comprehensive income (loss), net of tax	457					457
Dividends on Common Stock	(30,332)				(30,332)
Share-based compensation, shares		48,956	(20,497)
Share-based compensation	538	$ 49	$ 1,078	(589)
Issuance of common stock, shares		280,497
Issuance of common stock	19,999	$ 280		19,719
Issuance costs	(289)			(289)
Distributions to noncontrolling interest	(4,846)						(4,846)
Common Stock, Shares, Outstanding at Mar. 31, 2019		60,378,020	23,756
Total equity at Mar. 31, 2019	2,383,702	$ 60,378	$ (1,432)	1,469,410	777,262	(26,459)	104,543
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	3,390				3,390
Common Stock, Shares, Outstanding at Dec. 31, 2019		61,480,658	3,956
Total equity at Dec. 31, 2019	2,464,069	$ 61,481	$ (267)	1,552,788	778,776	(30,655)	101,946
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	97,224				93,174		4,050
Other comprehensive income (loss), net of tax	1,273					1,273
Dividends on Common Stock	(32,902)				(32,902)
Share-based compensation, shares		69,378	20,700
Share-based compensation	674	$ 69	$ (1,658)	2,263
Issuance of common stock, shares		1,222,942
Issuance of common stock	100,000	$ 1,223		98,777
Issuance costs	(967)			(967)
Distributions to noncontrolling interest	(4,741)						(4,741)
Common Stock, Shares, Outstanding at Mar. 31, 2020		62,772,978	24,656
Total equity at Mar. 31, 2020	2,624,423	$ 62,773	$ (1,925)	$ 1,652,861	838,841	$ (29,382)	$ 101,255
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (207)				$ (207)

Condensed Consolidated Statem_6

Condensed Consolidated Statements Of Equity (unaudited) Condensed Consolidated Statements of Equity (unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.535	$ 0.505

Management's Statement_

Management's Statement:	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Management's Statement	Management’s Statement The unaudited Condensed Consolidated Financial Statements included herein have been prepared by Black Hills Corporation (together with our subsidiaries the “Company”, “us”, “we” or “our”), pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted pursuant to such rules and regulations; however, we believe that the footnotes adequately disclose the information presented. These Condensed Consolidated Financial Statements should be read in conjunction with the consolidated financial statements and the notes included in our 2019 Annual Report on Form 10-K filed with the SEC. Segment Reporting We conduct our operations through the following reportable segments: Electric Utilities, Gas Utilities, Power Generation and Mining. Our reportable segments are based on our method of internal reporting, which is generally segregated by differences in products, services and regulation. All of our operations and assets are located within the United States. Use of Estimates and Basis of Presentation The information furnished in the accompanying Condensed Consolidated Financial Statements reflects certain estimates required and all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the March 31, 2020 , December 31, 2019 and March 31, 2019 financial information. Certain industries in which we operate are highly seasonal, and revenue from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Demand for electricity and natural gas is sensitive to seasonal cooling, heating and industrial load requirements. In particular, the normal peak usage season for electric utilities is June through August while the normal peak usage season for gas utilities is November through March. Significant earnings variances can be expected between the Gas Utilities segment’s peak and off-peak seasons. Due to this seasonal nature, our results of operations for the three months ended March 31, 2020 and March 31, 2019 , and our financial condition as of March 31, 2020 and December 31, 2019 are not necessarily indicative of the results of operations and financial condition to be expected for any other period. All earnings per share amounts discussed refer to diluted earnings per share unless otherwise noted. Reclassification We changed certain classifications of operating expenses on the Consolidated Statements of Income for the three months ended March 31, 2019. Amounts previously reported as Operations and maintenance, Taxes - property and production, and Other operating expenses of ($0.3) million , ($0.3) million , and ($0.4) million , respectively, have been reclassified to Fuel, purchased power and cost of natural gas sold to conform with current year presentation. The prior year reclassifications did not impact previously reported operating income or net income. COVID-19 Pandemic In March 2020, the World Health Organization categorized COVID-19 as a pandemic and the President of the United States declared the outbreak a national emergency. The U.S. government has deemed the electric and natural gas utilities as “critical” in providing essential services during this emergency. As a provider of critical services, the Company has an obligation to provide services to our customers. The Company remains focused on protecting the health of its employees and the communities in which it operates while assuring the continuity of its business operations. The Company’s Condensed Consolidated Financial Statements reflect estimates and assumptions made by management that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the Condensed Consolidated Financial Statements and reported amounts of revenue and expenses during the reporting periods presented. The Company considered the impacts of COVID-19 on the assumptions and estimates used and determined that for the three months ended March 31, 2020, there were no material adverse impacts on the Company’s results of operations. Change in Accounting Principle - Pension Accounting Asset Method Effective January 1, 2020, we changed our method of accounting for net periodic benefit cost. Prior to the change, the Company used a calculated value for determining market-related value of plan assets which amortized the effects of gains and losses over a five-year period. Effective with the accounting change, the Company will continue to use a calculated value for the return-seeking assets (equities) in the portfolio and change to fair value for the liability-hedging assets (fixed income). See Note 12 for additional information. Recently Issued Accounting Standards Simplifying the Accounting for Income Taxes, ASU 2019-12 In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes as part of its overall simplification initiative to reduce costs and complexity in applying accounting standards while maintaining or improving the usefulness of the information provided to users of the financial statements. Amendments include removal of certain exceptions to the general principles of ASC 740, Income Taxes, and simplification in several other areas such as accounting for a franchise tax (or similar tax) that is partially based on income. The new guidance is effective for interim and annual periods beginning after December 15, 2020 with early adoption permitted. We are currently reviewing this standard to assess the impact on our financial position, results of operations and cash flows. Recently Adopted Accounting Standards Financial Instruments -- Credit Losses: Measurement of Credit Losses on Financial Instruments, ASU 2016-13 In June 2016, the FASB issued ASU 2016-13, Financial Instruments -- Credit Losses: Measurement of Credit Losses on Financial Instruments, which was subsequently amended by ASU 2018-19, ASU 2019-04, 2019-05, 2019-10, and 2019-11. The standard introduces new accounting guidance for credit losses on financial instruments within its scope, including trade receivables. This new guidance adds an impairment model that is based on expected losses rather than incurred losses. We adopted this standard on January 1, 2020 with prior year comparative financial information remaining as previously reported when transitioning to the new standard. On January 1, 2020, we recorded an increase to our allowance for credit losses, primarily associated with the inclusion of expected losses on unbilled revenue. The cumulative effect of the adoption, net of tax impact, was $0.2 million , which was recorded as an adjustment to retained earnings. Simplifying the Test for Goodwill Impairment, ASU 2017-04 In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment by eliminating step 2 from the goodwill impairment test. Under the new guidance, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss will be recognized in an amount equal to that excess, limited to the amount of goodwill allocated to that reporting unit. We adopted this standard prospectively on January 1, 2020. Adoption of this guidance is not expected to have an impact on our financial position, results of operations or cash flows. Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, ASU 2018-15 In August 2018, the FASB issued ASU 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligns the requirements for recording implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. As a result, certain categories of implementation costs that previously would have been charged to expense as incurred are now capitalized as prepayments and amortized over the term of the arrangement. We adopted this standard prospectively on January 1, 2020. Adoption of this guidance did not have a material impact on our financial position, results of operations or cash flows.

Revenue_

Revenue:	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Our revenue contracts generally provide for performance obligations that are: fulfilled and transfer control to customers over time; represent a series of distinct services that are substantially the same; involve the same pattern of transfer to the customer; and provide a right to consideration from our customers in an amount that corresponds directly with the value to the customer for the performance completed to date. Therefore, we recognize revenue in the amount to which we have a right to invoice. The following tables depict the disaggregation of revenue, including intercompany revenue, from contracts with customers by customer type and timing of revenue recognition for each of the reporting segments for the three months ended March 31, 2020 and 2019 . Sales tax and other similar taxes are excluded from revenues. Three Months Ended March 31, 2020 Electric Utilities Gas Utilities Power Generation Mining Inter-company Revenues Total Customer types: (in thousands) Retail $ 148,640 $ 298,247 $ — $ 14,403 $ (7,839 ) $ 453,451 Transportation — 44,108 — — (139 ) 43,969 Wholesale 5,552 — 25,467 — (23,612 ) 7,407 Market - off-system sales 4,867 138 — — (2,639 ) 2,366 Transmission/Other 14,857 12,572 — — (4,413 ) 23,016 Revenue from contracts with customers $ 173,916 $ 355,065 $ 25,467 $ 14,403 $ (38,642 ) $ 530,209 Other revenues 223 5,708 499 802 (391 ) 6,841 Total revenues $ 174,139 $ 360,773 $ 25,966 $ 15,205 $ (39,033 ) $ 537,050 Timing of revenue recognition: Services transferred at a point in time $ — $ — $ — $ 14,403 $ (7,839 ) $ 6,564 Services transferred over time 173,916 355,065 25,467 — (30,803 ) 523,645 Revenue from contracts with customers $ 173,916 $ 355,065 $ 25,467 $ 14,403 $ (38,642 ) $ 530,209 Three Months Ended March 31, 2019 Electric Utilities Gas Utilities Power Generation Mining Inter-company Revenues Total Customer Types: Retail $ 153,463 $ 354,275 $ — $ 15,829 $ (8,128 ) $ 515,439 Transportation — 44,517 — — (432 ) 44,085 Wholesale 8,343 — 24,147 — (21,891 ) 10,599 Market - off-system sales 6,692 217 — — (2,224 ) 4,685 Transmission/Other 14,175 13,190 — — (4,203 ) 23,162 Revenue from contracts with customers $ 182,673 $ 412,199 $ 24,147 $ 15,829 $ (36,878 ) $ 597,970 Other revenues 254 (1,119 ) 1,098 600 (993 ) (160 ) Total Revenues $ 182,927 $ 411,080 $ 25,245 $ 16,429 $ (37,871 ) $ 597,810 Timing of Revenue Recognition: Services transferred at a point in time $ — $ — $ — $ 15,829 $ (8,128 ) $ 7,701 Services transferred over time 182,673 412,199 24,147 — (28,750 ) 590,269 Revenue from contracts with customers $ 182,673 $ 412,199 $ 24,147 $ 15,829 $ (36,878 ) $ 597,970 Contract Balances The nature of our primary revenue contracts provides an unconditional right to consideration upon service delivery; therefore, no customer contract assets or liabilities exist. The unconditional right to consideration is represented by the balance in our Accounts Receivable further discussed in Note 4 . We do not typically incur costs that would be capitalized to obtain or fulfill a revenue contract.

Business Segment Information_

Business Segment Information:	3 Months Ended
	Mar. 31, 2020
Segment Reporting Information, Additional Information [Abstract]
Business Segment Information	Business Segment Information Our reportable segments are based on our method of internal reporting, which is generally segregated by differences in products, services and regulation. All of our operations and assets are located within the United States. Segment and Corporate and Other information is as follows (in thousands): Three Months Ended March 31, 2020 External Operating Revenue Inter-company Operating Revenue Total Revenues Contract Customers Other Revenues Contract Customers Other Revenues Segment: Electric Utilities $ 167,503 $ 223 $ 6,413 $ — $ 174,139 Gas Utilities 354,287 5,708 778 — 360,773 Power Generation 1,855 443 23,612 56 25,966 Mining 6,564 467 7,839 335 15,205 Inter-company eliminations — — (38,642 ) (391 ) (39,033 ) Total $ 530,209 $ 6,841 $ — $ — $ 537,050 Three Months Ended March 31, 2019 External Operating Revenue Inter-company Operating Revenue Total Revenues Contract Customers Other Revenues Contract Customers Other Revenues Segment: Electric Utilities $ 176,663 $ 254 $ 6,010 $ — $ 182,927 Gas Utilities 411,500 (1,119 ) 699 — 411,080 Power Generation 2,257 436 21,890 662 25,245 Mining 7,550 269 8,279 331 16,429 Inter-company eliminations — — (36,878 ) (993 ) (37,871 ) Total $ 597,970 $ (160 ) $ — $ — $ 597,810 Three Months Ended March 31, 2020 2019 Adjusted operating income (a) : Electric Utilities $ 35,650 $ 41,020 Gas Utilities 102,897 103,314 Power Generation 11,349 11,967 Mining 3,129 4,337 Corporate and Other 160 (507 ) Operating income 153,185 160,131 Interest expense, net (35,453 ) (34,717 ) Impairment of investment (6,859 ) — Other income (expense), net 2,353 (789 ) Income tax (expense) (16,002 ) (17,263 ) Net income 97,224 107,362 Net income attributable to noncontrolling interest (4,050 ) (3,554 ) Net income available for common stock $ 93,174 $ 103,808 __________ (a) Adjusted operating income recognizes intersegment revenues and costs for Colorado Electric’s PPA with Black Hills Colorado IPP on an accrual basis rather than as a finance lease. This presentation of segment information does not impact consolidated financial results. Segment and Corporate and Other balances included in the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands): Total assets (net of inter-company eliminations) as of: March 31, 2020 December 31, 2019 Segment: Electric Utilities $ 2,931,902 $ 2,900,983 Gas Utilities 4,043,539 4,032,339 Power Generation 412,572 417,715 Mining 80,289 77,175 Corporate and Other 180,512 130,245 Total assets $ 7,648,814 $ 7,558,457

Selected Balance Sheet Informat

Selected Balance Sheet Information:	3 Months Ended
	Mar. 31, 2020
Selected Balance Sheet Information [Abstract]
Selected Balance Sheet Information	Selected Balance Sheet Information Accounts Receivable Following is a summary of Accounts receivable, net included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Accounts receivable, trade $ 162,138 $ 144,747 Unbilled revenue 81,927 113,502 Less: Allowance for credit losses (5,162 ) (2,444 ) Accounts receivable, net $ 238,903 $ 255,805 The ongoing credit evaluation of our customers during the COVID-19 pandemic is further discussed in the Credit Risk section of Note 9 . The Company did not experience material credit losses or customer defaults during the three months ended March 31, 2020. Materials, Supplies and Fuel The following amounts by major classification are included in Materials, supplies and fuel on the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Materials and supplies $ 88,346 $ 82,809 Fuel - Electric Utilities 3,049 2,425 Natural gas in storage 1,499 31,938 Total materials, supplies and fuel $ 92,894 $ 117,172 Accrued Liabilities The following amounts by major classification are included in Accrued liabilities on the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Accrued employee compensation, benefits and withholdings $ 45,070 $ 62,837 Accrued property taxes 45,666 44,547 Customer deposits and prepayments 43,524 54,728 Accrued interest 43,776 31,868 Other (none of which is individually significant) 25,409 32,787 Total accrued liabilities $ 203,445 $ 226,767

Regulatory Matters_

Regulatory Matters:	3 Months Ended
	Mar. 31, 2020
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	Regulatory Matters We had the following regulatory assets and liabilities (in thousands) as of: March 31, 2020 December 31, 2019 Regulatory assets Deferred energy and fuel cost adjustments (a) $ 35,687 $ 34,088 Deferred gas cost adjustments (a) — 1,540 Gas price derivatives (a) 1,302 3,328 Deferred taxes on AFUDC (b) 7,739 7,790 Employee benefit plans (c) 117,150 115,900 Environmental (a) 1,439 1,454 Loss on reacquired debt (a) 24,299 24,777 Renewable energy standard adjustment (a) 340 1,622 Deferred taxes on flow through accounting (c) 44,589 41,220 Decommissioning costs (b) 10,248 10,670 Gas supply contract termination (a) 7,007 8,485 Other regulatory assets (a) 22,429 20,470 Total regulatory assets 272,229 271,344 Less current regulatory assets (49,415 ) (43,282 ) Regulatory assets, non-current $ 222,814 $ 228,062 Regulatory liabilities Deferred energy and gas costs (a) $ 40,002 $ 17,278 Employee benefit plan costs and related deferred taxes (c) 41,518 43,349 Cost of removal (a) 170,954 166,727 Excess deferred income taxes (c) 283,690 285,438 TCJA revenue reserve 5,147 3,418 Other regulatory liabilities (c) 17,183 20,442 Total regulatory liabilities 558,494 536,652 Less current regulatory liabilities (54,345 ) (33,507 ) Regulatory liabilities, non-current $ 504,149 $ 503,145 __________ (a) Recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base. Regulatory Activity Except as discussed below, there have been no other significant changes to our Regulatory Matters from those previously disclosed in Note 13 of the Notes to the Consolidated Financial Statements in our 2019 Annual Report on Form 10-K. Black Hills Wyoming and Wyoming Electric Wygen 1 FERC Filing Black Hills Wyoming has a PPA with Wyoming Electric expiring on December 31, 2022, which provides 60 MW of unit-contingent capacity and energy from Black Hills Wyoming’s Wygen I facility. On August 2, 2019, Black Hills Wyoming and Wyoming Electric jointly filed a request with FERC for approval of a new 60 MW PPA. The agreement would fulfill Wyoming Electric’s capacity need at the expiration of the current agreement on December 31, 2022. If approved, Black Hills Wyoming will continue to deliver 60 MW of energy to Wyoming Electric from its Wygen I power plant starting January 1, 2023, and continuing for an additional 20 years to December 31, 2042. On February 21, 2020, the FERC set this filing for hearing. However, the hearing has been placed in abeyance pending a FERC monitored settlement process. Settlement negotiations are ongoing among all parties. Any settlement would require FERC approval. To the extent the parties are unable to reach agreement, the next step in FERC’s process would be to set the matter for hearing. We will continue to evaluate our options to fulfill Wyoming Electric’s 60 MW capacity need. Colorado Gas Jurisdictional Consolidation and Rate Review On February 1, 2019, Colorado Gas filed a rate review with the CPUC requesting approval to consolidate rates, tariffs, and services of its two existing gas distribution territories. The rate review requested $2.5 million in new revenue to recover investments in safety, reliability and system integrity. Colorado Gas also requested a new rider mechanism to recover future safety and integrity investments in its system. On December 27, 2019, the ALJ issued a recommended decision denying the company’s plan to consolidate rate territories and rider mechanism and also recommended a rate decrease. On April 14, 2020, the CPUC deliberated on the ALJ’s recommended decision and filed exceptions to that decision. The CPUC essentially accepted the ALJ’s recommended decisions, except for return on equity, which they lowered from 9.5% to 9.2% . A final order and new rates are anticipated to be effective in the second quarter of 2020.

Earnings Per Share_

Earnings Per Share:	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share A reconciliation of share amounts used to compute earnings per share in the accompanying Condensed Consolidated Statements of Income was as follows (in thousands): Three Months Ended March 31, 2020 2019 Net income available for common stock $ 93,174 $ 103,808 Weighted average shares - basic 61,778 59,920 Dilutive effect of: Equity compensation 78 140 Weighted average shares - diluted 61,856 60,060 Earnings per share of common stock: Earnings per share, Basic $ 1.51 $ 1.73 Earnings per share, Diluted $ 1.51 $ 1.73 The following securities were excluded from the diluted earnings per share computation because of their anti-dilutive nature (in thousands): Three Months Ended March 31, 2020 2019 Equity compensation 12 6 Restricted stock 26 — Anti-dilutive shares 38 6

Notes Payable, Current Maturiti

Notes Payable, Current Maturities and Debt:	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Notes Payable, Current Maturities and Debt	Notes Payable, Current Maturities and Debt We had the following short-term debt outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Balance Outstanding Letters of Credit (a) Balance Outstanding Letters of Credit (a) Revolving Credit Facility $ 165,000 $ 17,281 $ — $ 30,274 CP Program 154,125 — 349,500 — Total $ 319,125 $ 17,281 $ 349,500 $ 30,274 _______________ (a) Letters of credit are off-balance sheet commitments that reduce the borrowing capacity available on our corporate Revolving Credit Facility. For the three months ended March 31, 2020, we utilized a combination of our $750 million Revolving Credit Facility and CP Program to meet our business needs and support our capital investment plan. Our net short-term borrowings (payments) during the three months ended March 31, 2020 were $(30) million . The weighted average interest rate on Revolving Credit Facility and CP Program borrowings at March 31, 2020 was 1.92% and 1.74% , respectively. Debt Covenants Under our Revolving Credit Facility and term loan agreements, we are required to maintain a Consolidated Indebtedness to Capitalization Ratio not to exceed 0.65 to 1.00 . Our Consolidated Indebtedness to Capitalization Ratio was calculated by dividing (i) consolidated indebtedness, which includes letters of credit and certain guarantees issued, by (ii) capital, which includes consolidated indebtedness plus consolidated net worth, which excludes noncontrolling interest in subsidiaries. Subject to applicable cure periods, a violation of any of these covenants would constitute an event of default that entitles the lenders to terminate their remaining commitments and accelerate all principal and interest outstanding. Our Revolving Credit Facility and term loans require compliance with the following financial covenant, which we were in compliance with at March 31, 2020: As of March 31, 2020 Covenant Requirement Consolidated Indebtedness to Capitalization Ratio 58.2% Less than 65% South Dakota Electric Series 94A Debt On March 24, 2020 South Dakota Electric paid off its $2.9 million , Series 94A variable rate notes due June 1, 2024. These notes were tendered by the sole investor on March 17, 2020.

Equity_

Equity:	3 Months Ended
	Mar. 31, 2020
Statement of Stockholders' Equity [Abstract]
Equity	Equity February 2020 Equity Issuance On February 27, 2020, we issued 1.2 million shares of common stock to a single investor through an underwritten registered transaction at a price of $81.77 per share for proceeds of $99 million , net of $1.0 million of issuance costs. The shares of common stock were offered pursuant to our shelf registration statement filed with the SEC. ATM Activity Our ATM allows us to sell shares of our common stock with an aggregate value of up to $300 million . The shares may be offered from time to time pursuant to a sales agreement dated August 4, 2017. Shares of common stock are offered pursuant to our shelf registration statement filed with the SEC. We did not issue any common shares during the three months ended March 31, 2020 under the ATM. During the three months ended March 31, 2019, we issued a total of 0.3 million shares of common stock under the ATM for proceeds of $20 million , net of $0.2 million in issuance costs.

Risk Management and Derivatives

Risk Management and Derivatives:	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Risk Management and Derivatives	Risk Management and Derivatives Market and Credit Risk Disclosures Our activities in the regulated and non-regulated energy sectors expose us to a number of risks in the normal operations of our businesses. Depending on the activity, we are exposed to varying degrees of market risk and credit risk. Market Risk Market risk is the potential loss that may occur as a result of an adverse change in market price, rate or supply. We are exposed to the following market risks, including, but not limited to: • Commodity price risk associated with our retail natural gas and wholesale electric power marketing activities, as well as our fuel procurement for several of our gas-fired generation assets, which include market fluctuations due to unpredictable factors such as the COVID-19 pandemic, weather, market speculation, pipeline constraints, and other factors that may impact natural gas and electric energy supply and demand; and • Interest rate risk associated with our variable debt. Credit Risk Credit risk is the risk of financial loss resulting from non-performance of contractual obligations by a counterparty. For production and generation activities, we attempt to mitigate our credit exposure by conducting business primarily with high credit quality entities, setting tenor and credit limits commensurate with counterparty financial strength, obtaining master netting agreements, and mitigating credit exposure with less creditworthy counterparties through parental guarantees, prepayments, letters of credit, and other security agreements. We perform ongoing credit evaluations of our customers and adjust credit limits based on payment history and the customer’s current creditworthiness, as determined by review of their current credit information. We maintain a provision for estimated credit losses based upon historical experience and any specific customer collection issue that is identified. Although we did not experience material credit losses or customer defaults for the three months ended March 31, 2020, we are monitoring COVID-19 impacts and changes to customer load, consistency in customer payments, requests for deferred or discounted payments, and requests for changes to credit limits to quantify future financial impacts to the allowance for credit losses. Derivatives and Hedging Activity Our derivative and hedging activities included in the accompanying Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Income and Condensed Consolidated Statements of Comprehensive Income are detailed below and in Note 10 . Utilities The operations of our utilities, including natural gas used by our Electric Utilities’ generation plants or those plants under PPAs where our Electric Utilities must provide the generation fuel (tolling agreements) and natural gas sold by our Gas Utilities, expose our utility customers to volatility in natural gas prices. Therefore, as allowed or required by state utility commissions, we have entered into commission-approved hedging programs utilizing natural gas futures, options, over-the-counter swaps and basis swaps to reduce our customers’ underlying exposure to these fluctuations. These transactions are considered derivatives, and in accordance with accounting standards for derivatives and hedging, mark-to-market adjustments are recorded as Derivative assets or Derivative liabilities on the accompanying Condensed Consolidated Balance Sheets, net of balance sheet offsetting as permitted by GAAP. For our regulated Utilities’ hedging plans, unrealized and realized gains and losses, as well as option premiums and commissions on these transactions are recorded as Regulatory assets or Regulatory liabilities in the accompanying Condensed Consolidated Balance Sheets in accordance with the state utility commission guidelines. When the related costs are recovered through our rates, the hedging activity is recognized in the Condensed Consolidated Statements of Income. We buy, sell and deliver natural gas at competitive prices by managing commodity price risk. As a result of these activities, this area of our business is exposed to risks associated with changes in the market price of natural gas. We manage our exposure to such risk using over-the-counter and exchange traded options and swaps with counterparties in anticipation of forecasted purchases and/or sales from April 2020 through May 2022. A portion of our over-the-counter swaps have been designated as cash flow hedges to mitigate the commodity price risk associated with deliveries under fixed price forward contracts to deliver gas to our Choice Gas Program customers. The effective portion of the gain or loss on these designated derivatives is reported in AOCI in the accompanying Condensed Consolidated Balance Sheets and the ineffective portion, if any, is reported in Fuel, purchased power and cost of natural gas sold. Effectiveness of our hedging position is evaluated at least quarterly. The contract or notional amounts and terms of the electric and natural gas derivative commodity instruments held at our Utilities are composed of both long and short positions. We had the following net long positions as of: March 31, 2020 December 31, 2019 Units Notional Amounts Maximum Term (months) (a) Notional Amounts Maximum Term (months) (a) Natural gas futures purchased MMBtus 920,000 9 1,450,000 12 Natural gas options purchased, net MMBtus — 0 3,240,000 3 Natural gas basis swaps purchased MMBtus 790,000 9 1,290,000 12 Natural gas over-the-counter swaps, net (b) MMBtus 4,620,000 26 4,600,000 24 Natural gas physical contracts, net (c) MMBtus 1,104,725 12 13,548,235 12 Electric wholesale contracts (c) MWh 195,825 9 — 0 __________ (a) Term reflects the maximum forward period hedged. (b) As of March 31, 2020 , 800,000 MMBtus of natural gas over-the-counter swaps purchases were designated as cash flow hedges. (c) Volumes exclude contracts that qualify for the normal purchases and normal sales exception. We have certain derivative contracts which contain credit provisions. These credit provisions may require the Company to post collateral when credit exposure to the Company is in excess of a negotiated line of unsecured credit. At March 31, 2020 , the Company posted $0.5 million related to such provisions, which is included in Other current assets on the Condensed Consolidated Balance Sheets. Derivatives by Balance Sheet Classification As required by accounting standards for derivatives and hedges, fair values within the following tables are presented on a gross basis aside from the netting of asset and liability positions. Netting of positions is permitted in accordance with accounting standards for offsetting and under terms of our master netting agreements that allow us to settle positive and negative positions. The following table presents the fair value and balance sheet classification of our derivative instruments (in thousands) as of: Balance Sheet Location March 31, 2020 December 31, 2019 Derivatives designated as hedges: Asset derivative instruments: Current commodity derivatives Derivative assets, current $ 8 $ 1 Noncurrent commodity derivatives Other assets, non-current — 3 Liability derivative instruments: Current commodity derivatives Derivative liabilities, current (284 ) (490 ) Noncurrent commodity derivatives Other deferred credits and other liabilities (10 ) (29 ) Total derivatives designated as hedges $ (286 ) $ (515 ) Derivatives not designated as hedges: Asset derivative instruments: Current commodity derivatives Derivative assets, current $ 1,772 $ 341 Noncurrent commodity derivatives Other assets, non-current 156 2 Liability derivative instruments: Current commodity derivatives Derivative liabilities, current (568 ) (1,764 ) Noncurrent commodity derivatives Other deferred credits and other liabilities (28 ) (63 ) Total derivatives not designated as hedges $ 1,332 $ (1,484 ) Derivatives Designated as Hedges The impacts of cash flow hedges on our Condensed Consolidated Statements of Comprehensive Income and Condensed Consolidated Statements of Income are presented below for the three months ended March 31, 2020 and 2019 . Note that this presentation does not reflect gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended March 31, Three Months Ended March 31, 2020 2019 2020 2019 Derivatives in Cash Flow Hedging Relationships Amount of (Gain)/Loss Recognized in OCI Income Statement Location Amount of Gain/(Loss) Reclassified from AOCI into Income (in thousands) (in thousands) Interest rate swaps $ 713 $ 713 Interest expense $ (713 ) $ (713 ) Commodity derivatives 257 (320 ) Fuel, purchased power and cost of natural gas sold (486 ) 554 Total $ 970 $ 393 $ (1,199 ) $ (159 ) Based on March 31, 2020 prices, a $0.3 million gain would be realized, reported in pre-tax earnings and reclassified from AOCI during the next 12 months. As market prices fluctuate, estimated and actual realized gains or losses will change during future periods. Derivatives Not Designated as Hedges The following table summarizes the impacts of derivative instruments not designated as hedge instruments on our Condensed Consolidated Statements of Income for the three months ended March 31, 2020 and 2019 . Note that this presentation does not reflect gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended March 31, 2020 2019 Derivatives Not Designated as Hedging Instruments Income Statement Location Amount of Gain/(Loss) on Derivatives Recognized in Income (in thousands) Commodity derivatives - Electric Fuel, purchased power and cost of natural gas sold $ 1,362 $ — Commodity derivatives - Natural Gas Fuel, purchased power and cost of natural gas sold 766 25 $ 2,128 $ 25 As discussed above, financial instruments used in our regulated utilities are not designated as cash flow hedges. There is no earnings impact for our Gas Utilities because the unrealized gains and losses arising from the use of these financial instruments are recorded as Regulatory assets or Regulatory liabilities. The net unrealized losses included in our Regulatory asset or Regulatory liability accounts related to the hedges in our Gas Utilities were $1.3 million and $3.3 million as of March 31, 2020 and December 31, 2019 , respectively. For our Electric Utilities, the unrealized gains and losses arising from these derivatives are recognized in the Consolidated Statements of Income.

Fair Value Measurements_

Fair Value Measurements:	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We use the following fair value hierarchy for determining inputs for our financial instruments. Our assets and liabilities for financial instruments are classified and disclosed in one of the following fair value categories: Level 1 — Unadjusted quoted prices available in active markets that are accessible at the measurement date for identical unrestricted assets or liabilities. Level 1 instruments primarily consist of highly liquid and actively traded financial instruments with quoted pricing information on an ongoing basis. Level 2 — Pricing inputs include quoted prices for identical or similar assets and liabilities in active markets other than quoted prices in Level 1, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability and inputs that are derived principally from or corroborated by observable market data by correlation or other means. Level 3 — Pricing inputs are generally less observable from objective sources. These inputs reflect management’s best estimate of fair value using its own assumptions about the assumptions a market participant would use in pricing the asset or liability. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the placement within the fair value hierarchy levels. We record transfers, if necessary, between levels at the end of the reporting period for all of our financial instruments. Transfers into Level 3, if any, occur when significant inputs used to value the derivative instruments become less observable, such as a significant decrease in the frequency and volume in which the instrument is traded, negatively impacting the availability of observable pricing inputs. Transfers out of Level 3, if any, occur when the significant inputs become more observable, such as when the time between the valuation date and the delivery date of a transaction becomes shorter, positively impacting the availability of observable pricing inputs. Recurring Fair Value Measurements Derivatives The commodity contracts for our Utilities segments are valued using the market approach and include forward strip pricing at liquid delivery points, exchange-traded futures, options, basis swaps and over-the-counter swaps and options (Level 2) for wholesale electric energy and natural gas contracts. For exchange-traded futures, options and basis swap assets and liabilities, fair value was derived using broker quotes validated by the exchange settlement pricing for the applicable contract. For over-the-counter instruments, the fair value is obtained by utilizing a nationally recognized service that obtains observable inputs to compute the fair value, which we validate by comparing our valuation with the counterparty. The fair value of these swaps includes a CVA based on the credit spreads of the counterparties when we are in an unrealized gain position or on our own credit spread when we are in an unrealized loss position. For additional information, see Note 1 to the Consolidated Financial Statements included in our 2019 Annual Report on Form 10-K filed with the SEC. As of March 31, 2020 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Gas Utilities $ — $ 1,949 $ — $ (13 ) $ 1,936 Commodity derivatives — Electric Utilities — 1,362 — — 1,362 Total $ — $ 3,311 $ — $ (13 ) $ 3,298 Liabilities: Commodity derivatives — Gas Utilities $ — $ 2,464 $ — $ (1,573 ) $ 891 Total $ — $ 2,464 $ — $ (1,573 ) $ 891 As of December 31, 2019 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Gas Utilities $ — $ 1,433 $ — $ (1,085 ) $ 348 Total $ — $ 1,433 $ — $ (1,085 ) $ 348 Liabilities: Commodity derivatives — Gas Utilities $ — $ 5,254 $ — $ (2,909 ) $ 2,345 Total $ — $ 5,254 $ — $ (2,909 ) $ 2,345 Pension and Postretirement Plan Assets Fair value measurements also apply to the valuation of our pension and postretirement plan assets. Current accounting guidance requires employers to annually disclose information about the fair value measurements of their assets of a defined benefit pension or other postretirement plan. The fair value of these assets is presented in Note 18 to the Consolidated Financial Statements included in our 2019 Annual Report on Form 10-K. The Company has concluded that the market volatility associated with COVID-19 does not require interim re-measurement of our pension plan assets or defined benefit obligations. See Note 12 for additional information. Nonrecurring Fair Value Measurement A discussion of the fair value of our investment in equity securities of a privately held oil and gas company, a Level 3 asset, is included in Note 15 . Other fair value measures The following table presents the carrying amounts and fair values of financial instruments not recorded at fair value on the Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current maturities (a) $ 3,142,630 $ 3,320,562 $ 3,145,839 $ 3,479,367 __________ (a) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified as Level 2 in the fair value hierarchy. Carrying amount of long-term debt is net of deferred financing costs.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss):	3 Months Ended
	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) We record deferred gains (losses) in AOCI related to interest rate swaps designated as cash flow hedges, commodity contracts designated as cash flow hedges and the amortization of components of our defined benefit plans. Deferred gains (losses) for our commodity contracts designated as cash flow hedges are recognized in earnings upon settlement, while deferred gains (losses) related to our interest rate swaps are recognized in earnings as they are amortized. The following table details reclassifications out of AOCI and into net income. The amounts in parentheses below indicate decreases to net income in the Condensed Consolidated Statements of Income for the period (in thousands): Location on the Condensed Consolidated Statements of Income Amount Reclassified from AOCI Three Months Ended March 31, 2020 2019 Gains and (losses) on cash flow hedges: Interest rate swaps Interest expense $ (713 ) $ (713 ) Commodity contracts Fuel, purchased power and cost of natural gas sold (486 ) 554 (1,199 ) (159 ) Income tax Income tax benefit (expense) 285 35 Total reclassification adjustments related to cash flow hedges, net of tax $ (914 ) $ (124 ) Amortization of components of defined benefit plans: Prior service cost Operations and maintenance $ 30 $ 19 Actuarial gain (loss) Operations and maintenance (597 ) (220 ) (567 ) (201 ) Income tax Income tax benefit (expense) 88 48 Total reclassification adjustments related to defined benefit plans, net of tax $ (479 ) $ (153 ) Total reclassifications $ (1,393 ) $ (277 ) Balances by classification included within AOCI, net of tax on the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands): Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total As of December 31, 2019 $ (15,122 ) $ (456 ) $ (15,077 ) $ (30,655 ) Other comprehensive income (loss) before reclassifications — (175 ) 55 (120 ) Amounts reclassified from AOCI 543 371 479 1,393 As of March 31, 2020 $ (14,579 ) $ (260 ) $ (14,543 ) $ (29,382 ) Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total As of December 31, 2018 $ (17,307 ) $ 328 $ (9,937 ) $ (26,916 ) Other comprehensive income (loss) before reclassifications — 180 — 180 Amounts reclassified from AOCI 550 (426 ) 153 277 As of March 31, 2019 $ (16,757 ) $ 82 $ (9,784 ) $ (26,459 )

Employee Benefit Plans_

Employee Benefit Plans:	3 Months Ended
	Mar. 31, 2020
Defined Benefit Plan [Abstract]
Employee Benefit Plans	Employee Benefit Plans Change in Accounting Principle - Pension Accounting Asset Method Effective January 1, 2020, the Company changed its method of accounting for net periodic benefit cost. Prior to the change, the Company used a calculated value for determining market-related value of plan assets which amortized the effects of gains and losses over a five-year period. Effective with the accounting change, the Company will continue to use a calculated value for the return-seeking assets (equities) in the portfolio and fair value for the liability-hedging assets (fixed income). The Company considers the fair value method for determining market-related value of liability-hedging assets to be a preferable method of accounting because asset-related gains and losses are subject to amortization into pension cost immediately. Additionally, the fair value for liability-hedging assets allows for the impact of gains and losses on this portion of the asset portfolio to be reflected in tandem with changes in the liability which is linked to changes in the discount rate assumption for re-measurement. We evaluated the effect of this change in accounting method and deemed it immaterial to the historical and current financial statements and therefore did not account for the change retrospectively. Accordingly, the Company calculated the cumulative difference using a calculated value versus fair value to determine market-related value for liability-hedging assets of the portfolio. The cumulative effect of this change, as of January 1, 2020, resulted in a decrease to prior service costs, as recorded in Other income (expense), net, of $0.6 million , an increase in Income tax expense of $0.2 million and an increase to Net income of $0.4 million within the accompanying Condensed Consolidated Statements of Income for the three months ended March 31, 2020. Funding Status of Employee Benefit Plans Based on the fair value of assets and estimated discount rate used to value benefit obligations as of March 31, 2020, we estimate the unfunded status of our employee benefit plans to be approximately $46 million compared to $51 million at December 31, 2019. The Company has concluded that the market volatility associated with COVID-19 does not require interim re-measurement of our pension plan assets or defined benefit obligations. Defined Benefit Pension Plan The components of net periodic benefit cost for the Defined Benefit Pension Plan were as follows (in thousands): Three Months Ended March 31, 2020 2019 Service cost $ 1,353 $ 1,346 Interest cost 3,357 4,343 Expected return on plan assets (5,648 ) (6,100 ) Prior service cost (benefit) — 6 Net loss (gain) 2,093 941 Net periodic benefit cost $ 1,155 $ 536 Defined Benefit Postretirement Healthcare Plan The components of net periodic benefit cost for the Defined Benefit Postretirement Healthcare Plan were as follows (in thousands): Three Months Ended March 31, 2020 2019 Service cost $ 514 $ 454 Interest cost 412 560 Expected return on plan assets (45 ) (57 ) Prior service cost (benefit) (137 ) (99 ) Net loss (gain) 5 — Net periodic benefit cost $ 749 $ 858 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit and Defined Contribution Plans were as follows (in thousands): Three Months Ended March 31, 2020 2019 Service cost $ (1,370 ) $ 1,285 Interest cost 275 324 Net loss (gain) 426 134 Net periodic benefit cost $ (669 ) $ 1,743 Contributions Contributions to the Defined Benefit Pension Plan are cash contributions made directly to the Pension Plan Trust account. Contributions to the Postretirement Healthcare and Supplemental Plans are made in the form of benefit payments. Contributions made in the first quarter of 2020 and anticipated contributions for 2020 and 2021 are as follows (in thousands): Contributions Made Additional Contributions Contributions Three Months Ended March 31, 2020 Anticipated for 2020 Anticipated for 2021 Defined Benefit Pension Plan $ — $ 12,700 $ 12,700 Non-pension Defined Benefit Postretirement Healthcare Plans $ 1,335 $ 4,006 $ 5,364 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans $ 355 $ 1,065 $ 1,614

Commitments and Contingencies_

Commitments and Contingencies:	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies There have been no significant changes to commitments and contingencies from those previously disclosed in Note 19 of our Notes to the Consolidated Financial Statements in our 2019 Annual Report on Form 10-K except for those described below. Future Purchase Agreement - Black Hills Wyoming and Wyoming Electric Black Hills Wyoming has a PPA with Wyoming Electric expiring on December 31, 2022, which provides 60 MW of unit-contingent capacity and energy from Black Hills Wyoming’s Wygen I facility. On August 2, 2019, Black Hills Wyoming and Wyoming Electric jointly filed a request with FERC for approval of a new 60 MW PPA. On February 21, 2020, the FERC set this filing for hearing. However, the hearing has been placed in abeyance pending a FERC monitored settlement process. Settlement negotiations are ongoing among all parties. Any settlement would require FERC approval. To the extent the parties are unable to reach agreement, the next step in FERC’s process would be to set the matter for hearing. See Note 5 for additional information.

Income Taxes_

Income Taxes:	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes CARES Act On March 27, 2020, the President signed the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”), which contained in part, an allowance for deferral of the employer portion of Social Security employment tax liabilities until 2021 and 2022, as well as a COVID-19 employee retention tax credit of up to $5,000 per eligible employee. Eligible employers are taxpayers experiencing either: (1) a full or partial suspension of business operations stemming from a government COVID-19-related order or (2) a more than 50% drop in gross receipts compared to the corresponding calendar quarter in 2019. This 50% employee retention tax credit applies to up to $10,000 in qualified wages paid between March 13, 2020 through December 31, 2020, and is refundable to the extent it exceeds the employer portion of payroll tax liability. Eligible wages or employer-paid health benefits must be paid for the period of time during which an employee did not provide services. However, employees do not need to stop providing all services to the employer for the credit to potentially apply. Additionally, the CARES Act accelerates the amount of alternative minimum tax (“AMT”) credits that can be refunded for the 2018 and 2019 annual tax returns. Based on the timing of the CARES Act, for the three months ended March 31, 2020, the related tax benefits from the CARES Act were not material. We are currently reviewing the potential future benefits related to employee retention tax credits and the payroll tax deferral provision to assess the impact on our financial position, results of operations and cash flows. Income tax (expense) for the Three Months Ended March 31, 2020 Compared to the Three Months Ended March 31, 2019 . Income tax benefit (expense) for the three months ended March 31, 2020 was $(16) million compared to $(17) million reported for the same period in 2019 . For the three months ended March 31, 2020 the effective tax rate was 14.1% compared to 13.9% for the same period in 2019. The higher effective tax rate is primarily due to a discrete tax adjustment related to the impairment of our investment in equity securities of a privately held oil and gas company partially offset by increased tax benefits from forecasted federal production tax credits associated with new wind assets.

Investments_

Investments:	3 Months Ended
	Mar. 31, 2020
Investments, All Other Investments [Abstract]
Investments	Investments In February 2018, we contributed $28 million of assets in exchange for equity securities in a privately held oil and gas company as we divested our Oil and Gas segment. The carrying value of our investment in the equity securities was recorded at cost. We review this investment on a periodic basis to determine whether a significant event or change in circumstances has occurred that may have an adverse effect on the value of the investment. During the third quarter of 2019, we assessed our investment for impairment as a result of a deterioration in earnings performance of the privately held oil and gas company and an adverse change in future natural gas prices. We engaged a third-party valuation consultant to estimate the fair value of our investment. The valuation was primarily based on an income approach but also considered a market valuation approach. The significant inputs used to estimate the fair value were the oil and gas reserve quantities and values utilizing forward market price curves, industry standard reserve adjustment factors and a discount rate of 10% . Based on the results of the valuation, we concluded that the carrying value of the investment exceeded fair value. As a result, we recorded a pre-tax impairment loss of $20 million for the three months ended September 30, 2019, which was the difference between the carrying amount and the fair value of the investment at that time. During the first quarter of 2020, we assessed our investment for impairment as a result of continued adverse changes in future natural gas prices and liquidity concerns at the privately held oil and gas company. We performed an internal analysis to compute the fair value of our investment, utilizing a consistent methodology as applied during the third quarter of 2019. Based on the results of the valuation, we concluded that the carrying value of the investment exceeded fair value. As a result, we recorded a pre-tax impairment loss of $6.9 million for the three months ended March 31, 2020, which was the difference between the carrying amount and the fair value of the investment at March 31, 2020. The following table presents the carrying value of our investments (in thousands) as of: March 31, 2020 December 31, 2019 Investment in privately held oil and gas company $ 1,500 $ 8,359 Cash surrender value of life insurance contracts 13,235 13,056 Other investments 515 514 Total investments $ 15,250 $ 21,929

Subsequent Events_

Subsequent Events:	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events We evaluated all subsequent event activity and concluded that no subsequent events have occurred that would require recognition in the condensed consolidated financial statements or disclosures, with the exception of the Note 5 disclosure surrounding Colorado Gas’ jurisdictional consolidation and rate review. There are many uncertainties regarding the COVID-19 pandemic, and the Company is closely monitoring the impact of the pandemic on all aspects of its business, including how it will impact its customers, employees, suppliers, vendors, and business partners. We are unable to predict the impact that COVID-19 will have on our financial position and operating results due to numerous uncertainties. The Company expects to continue to assess the evolving impact of COVID-19 and intends to make adjustments to its responses accordingly.

Management's Statement (Policie

Management's Statement (Policies)	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Segment Reporting	Segment Reporting We conduct our operations through the following reportable segments: Electric Utilities, Gas Utilities, Power Generation and Mining. Our reportable segments are based on our method of internal reporting, which is generally segregated by differences in products, services and regulation. All of our operations and assets are located within the United States.
Use of Estimates and Basis of Presentation	Use of Estimates and Basis of Presentation The information furnished in the accompanying Condensed Consolidated Financial Statements reflects certain estimates required and all adjustments, including accruals, which are, in the opinion of management, necessary for a fair presentation of the March 31, 2020 , December 31, 2019 and March 31, 2019 financial information. Certain industries in which we operate are highly seasonal, and revenue from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Demand for electricity and natural gas is sensitive to seasonal cooling, heating and industrial load requirements. In particular, the normal peak usage season for electric utilities is June through August while the normal peak usage season for gas utilities is November through March. Significant earnings variances can be expected between the Gas Utilities segment’s peak and off-peak seasons. Due to this seasonal nature, our results of operations for the three months ended March 31, 2020 and March 31, 2019 , and our financial condition as of March 31, 2020 and December 31, 2019 are not necessarily indicative of the results of operations and financial condition to be expected for any other period. All earnings per share amounts discussed refer to diluted earnings per share unless otherwise noted.
Reclassification, Policy	Reclassification We changed certain classifications of operating expenses on the Consolidated Statements of Income for the three months ended March 31, 2019. Amounts previously reported as Operations and maintenance, Taxes - property and production, and Other operating expenses of ($0.3) million , ($0.3) million , and ($0.4) million , respectively, have been reclassified to Fuel, purchased power and cost of natural gas sold to conform with current year presentation. The prior year reclassifications did not impact previously reported operating income or net income.
Change in Accounting Principle - Pension Accounting Asset Method	Change in Accounting Principle - Pension Accounting Asset Method Effective January 1, 2020, we changed our method of accounting for net periodic benefit cost. Prior to the change, the Company used a calculated value for determining market-related value of plan assets which amortized the effects of gains and losses over a five-year period. Effective with the accounting change, the Company will continue to use a calculated value for the return-seeking assets (equities) in the portfolio and change to fair value for the liability-hedging assets (fixed income). See Note 12 for additional information.
Recently Issued and Adopted Accounting Standards	Recently Issued Accounting Standards Simplifying the Accounting for Income Taxes, ASU 2019-12 In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes as part of its overall simplification initiative to reduce costs and complexity in applying accounting standards while maintaining or improving the usefulness of the information provided to users of the financial statements. Amendments include removal of certain exceptions to the general principles of ASC 740, Income Taxes, and simplification in several other areas such as accounting for a franchise tax (or similar tax) that is partially based on income. The new guidance is effective for interim and annual periods beginning after December 15, 2020 with early adoption permitted. We are currently reviewing this standard to assess the impact on our financial position, results of operations and cash flows. Recently Adopted Accounting Standards Financial Instruments -- Credit Losses: Measurement of Credit Losses on Financial Instruments, ASU 2016-13 In June 2016, the FASB issued ASU 2016-13, Financial Instruments -- Credit Losses: Measurement of Credit Losses on Financial Instruments, which was subsequently amended by ASU 2018-19, ASU 2019-04, 2019-05, 2019-10, and 2019-11. The standard introduces new accounting guidance for credit losses on financial instruments within its scope, including trade receivables. This new guidance adds an impairment model that is based on expected losses rather than incurred losses. We adopted this standard on January 1, 2020 with prior year comparative financial information remaining as previously reported when transitioning to the new standard. On January 1, 2020, we recorded an increase to our allowance for credit losses, primarily associated with the inclusion of expected losses on unbilled revenue. The cumulative effect of the adoption, net of tax impact, was $0.2 million , which was recorded as an adjustment to retained earnings. Simplifying the Test for Goodwill Impairment, ASU 2017-04 In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment by eliminating step 2 from the goodwill impairment test. Under the new guidance, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss will be recognized in an amount equal to that excess, limited to the amount of goodwill allocated to that reporting unit. We adopted this standard prospectively on January 1, 2020. Adoption of this guidance is not expected to have an impact on our financial position, results of operations or cash flows. Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, ASU 2018-15 In August 2018, the FASB issued ASU 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligns the requirements for recording implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. As a result, certain categories of implementation costs that previously would have been charged to expense as incurred are now capitalized as prepayments and amortized over the term of the arrangement. We adopted this standard prospectively on January 1, 2020. Adoption of this guidance did not have a material impact on our financial position, results of operations or cash flows.
Revenue Recognition	The nature of our primary revenue contracts provides an unconditional right to consideration upon service delivery; therefore, no customer contract assets or liabilities exist. The unconditional right to consideration is represented by the balance in our Accounts Receivable further discussed in Note 4 . We do not typically incur costs that would be capitalized to obtain or fulfill a revenue contract.

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables depict the disaggregation of revenue, including intercompany revenue, from contracts with customers by customer type and timing of revenue recognition for each of the reporting segments for the three months ended March 31, 2020 and 2019 . Sales tax and other similar taxes are excluded from revenues. Three Months Ended March 31, 2020 Electric Utilities Gas Utilities Power Generation Mining Inter-company Revenues Total Customer types: (in thousands) Retail $ 148,640 $ 298,247 $ — $ 14,403 $ (7,839 ) $ 453,451 Transportation — 44,108 — — (139 ) 43,969 Wholesale 5,552 — 25,467 — (23,612 ) 7,407 Market - off-system sales 4,867 138 — — (2,639 ) 2,366 Transmission/Other 14,857 12,572 — — (4,413 ) 23,016 Revenue from contracts with customers $ 173,916 $ 355,065 $ 25,467 $ 14,403 $ (38,642 ) $ 530,209 Other revenues 223 5,708 499 802 (391 ) 6,841 Total revenues $ 174,139 $ 360,773 $ 25,966 $ 15,205 $ (39,033 ) $ 537,050 Timing of revenue recognition: Services transferred at a point in time $ — $ — $ — $ 14,403 $ (7,839 ) $ 6,564 Services transferred over time 173,916 355,065 25,467 — (30,803 ) 523,645 Revenue from contracts with customers $ 173,916 $ 355,065 $ 25,467 $ 14,403 $ (38,642 ) $ 530,209 Three Months Ended March 31, 2019 Electric Utilities Gas Utilities Power Generation Mining Inter-company Revenues Total Customer Types: Retail $ 153,463 $ 354,275 $ — $ 15,829 $ (8,128 ) $ 515,439 Transportation — 44,517 — — (432 ) 44,085 Wholesale 8,343 — 24,147 — (21,891 ) 10,599 Market - off-system sales 6,692 217 — — (2,224 ) 4,685 Transmission/Other 14,175 13,190 — — (4,203 ) 23,162 Revenue from contracts with customers $ 182,673 $ 412,199 $ 24,147 $ 15,829 $ (36,878 ) $ 597,970 Other revenues 254 (1,119 ) 1,098 600 (993 ) (160 ) Total Revenues $ 182,927 $ 411,080 $ 25,245 $ 16,429 $ (37,871 ) $ 597,810 Timing of Revenue Recognition: Services transferred at a point in time $ — $ — $ — $ 15,829 $ (8,128 ) $ 7,701 Services transferred over time 182,673 412,199 24,147 — (28,750 ) 590,269 Revenue from contracts with customers $ 182,673 $ 412,199 $ 24,147 $ 15,829 $ (36,878 ) $ 597,970

Business Segment Information (T

Business Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
Segment Reporting Information, Additional Information [Abstract]
Segment Reporting	Segment and Corporate and Other information is as follows (in thousands): Three Months Ended March 31, 2020 External Operating Revenue Inter-company Operating Revenue Total Revenues Contract Customers Other Revenues Contract Customers Other Revenues Segment: Electric Utilities $ 167,503 $ 223 $ 6,413 $ — $ 174,139 Gas Utilities 354,287 5,708 778 — 360,773 Power Generation 1,855 443 23,612 56 25,966 Mining 6,564 467 7,839 335 15,205 Inter-company eliminations — — (38,642 ) (391 ) (39,033 ) Total $ 530,209 $ 6,841 $ — $ — $ 537,050 Three Months Ended March 31, 2019 External Operating Revenue Inter-company Operating Revenue Total Revenues Contract Customers Other Revenues Contract Customers Other Revenues Segment: Electric Utilities $ 176,663 $ 254 $ 6,010 $ — $ 182,927 Gas Utilities 411,500 (1,119 ) 699 — 411,080 Power Generation 2,257 436 21,890 662 25,245 Mining 7,550 269 8,279 331 16,429 Inter-company eliminations — — (36,878 ) (993 ) (37,871 ) Total $ 597,970 $ (160 ) $ — $ — $ 597,810 Three Months Ended March 31, 2020 2019 Adjusted operating income (a) : Electric Utilities $ 35,650 $ 41,020 Gas Utilities 102,897 103,314 Power Generation 11,349 11,967 Mining 3,129 4,337 Corporate and Other 160 (507 ) Operating income 153,185 160,131 Interest expense, net (35,453 ) (34,717 ) Impairment of investment (6,859 ) — Other income (expense), net 2,353 (789 ) Income tax (expense) (16,002 ) (17,263 ) Net income 97,224 107,362 Net income attributable to noncontrolling interest (4,050 ) (3,554 ) Net income available for common stock $ 93,174 $ 103,808 __________ (a) Adjusted operating income recognizes intersegment revenues and costs for Colorado Electric’s PPA with Black Hills Colorado IPP on an accrual basis rather than as a finance lease. This presentation of segment information does not impact consolidated financial results.
Reconciliation of Assets from Segment to Consolidated	Segment and Corporate and Other balances included in the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands): Total assets (net of inter-company eliminations) as of: March 31, 2020 December 31, 2019 Segment: Electric Utilities $ 2,931,902 $ 2,900,983 Gas Utilities 4,043,539 4,032,339 Power Generation 412,572 417,715 Mining 80,289 77,175 Corporate and Other 180,512 130,245 Total assets $ 7,648,814 $ 7,558,457

Selected Balance Sheet Inform_2

Selected Balance Sheet Information (Tables)	3 Months Ended
	Mar. 31, 2020
Selected Balance Sheet Information [Abstract]
Account Receivable Schedule	Following is a summary of Accounts receivable, net included in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Accounts receivable, trade $ 162,138 $ 144,747 Unbilled revenue 81,927 113,502 Less: Allowance for credit losses (5,162 ) (2,444 ) Accounts receivable, net $ 238,903 $ 255,805
Materials, Supplies, and Fuel Schedule	The following amounts by major classification are included in Materials, supplies and fuel on the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Materials and supplies $ 88,346 $ 82,809 Fuel - Electric Utilities 3,049 2,425 Natural gas in storage 1,499 31,938 Total materials, supplies and fuel $ 92,894 $ 117,172
Accrued Liabilities Schedule	The following amounts by major classification are included in Accrued liabilities on the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Accrued employee compensation, benefits and withholdings $ 45,070 $ 62,837 Accrued property taxes 45,666 44,547 Customer deposits and prepayments 43,524 54,728 Accrued interest 43,776 31,868 Other (none of which is individually significant) 25,409 32,787 Total accrued liabilities $ 203,445 $ 226,767

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2020
Regulatory Assets and Liabilities Disclosure [Abstract]
Schedule of Regulatory Assets and Liabilities	We had the following regulatory assets and liabilities (in thousands) as of: March 31, 2020 December 31, 2019 Regulatory assets Deferred energy and fuel cost adjustments (a) $ 35,687 $ 34,088 Deferred gas cost adjustments (a) — 1,540 Gas price derivatives (a) 1,302 3,328 Deferred taxes on AFUDC (b) 7,739 7,790 Employee benefit plans (c) 117,150 115,900 Environmental (a) 1,439 1,454 Loss on reacquired debt (a) 24,299 24,777 Renewable energy standard adjustment (a) 340 1,622 Deferred taxes on flow through accounting (c) 44,589 41,220 Decommissioning costs (b) 10,248 10,670 Gas supply contract termination (a) 7,007 8,485 Other regulatory assets (a) 22,429 20,470 Total regulatory assets 272,229 271,344 Less current regulatory assets (49,415 ) (43,282 ) Regulatory assets, non-current $ 222,814 $ 228,062 Regulatory liabilities Deferred energy and gas costs (a) $ 40,002 $ 17,278 Employee benefit plan costs and related deferred taxes (c) 41,518 43,349 Cost of removal (a) 170,954 166,727 Excess deferred income taxes (c) 283,690 285,438 TCJA revenue reserve 5,147 3,418 Other regulatory liabilities (c) 17,183 20,442 Total regulatory liabilities 558,494 536,652 Less current regulatory liabilities (54,345 ) (33,507 ) Regulatory liabilities, non-current $ 504,149 $ 503,145 __________ (a) Recovery of costs, but we are not allowed a rate of return. (b) In addition to recovery of costs, we are allowed a rate of return. (c) In addition to recovery or repayment of costs, we are allowed a return on a portion of this amount or a reduction in rate base.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share Reconciliation	A reconciliation of share amounts used to compute earnings per share in the accompanying Condensed Consolidated Statements of Income was as follows (in thousands): Three Months Ended March 31, 2020 2019 Net income available for common stock $ 93,174 $ 103,808 Weighted average shares - basic 61,778 59,920 Dilutive effect of: Equity compensation 78 140 Weighted average shares - diluted 61,856 60,060 Earnings per share of common stock: Earnings per share, Basic $ 1.51 $ 1.73 Earnings per share, Diluted $ 1.51 $ 1.73
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following securities were excluded from the diluted earnings per share computation because of their anti-dilutive nature (in thousands): Three Months Ended March 31, 2020 2019 Equity compensation 12 6 Restricted stock 26 — Anti-dilutive shares 38 6

Notes Payable, Current Maturi_2

Notes Payable, Current Maturities and Debt (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of Short-term Debt	We had the following short-term debt outstanding in the accompanying Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Balance Outstanding Letters of Credit (a) Balance Outstanding Letters of Credit (a) Revolving Credit Facility $ 165,000 $ 17,281 $ — $ 30,274 CP Program 154,125 — 349,500 — Total $ 319,125 $ 17,281 $ 349,500 $ 30,274 _______________ (a) Letters of credit are off-balance sheet commitments that reduce the borrowing capacity available on our corporate Revolving Credit Facility.

Risk Management and Derivativ_2

Risk Management and Derivatives (Tables)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Contract or notional amounts and terms of marketing activities and derivative commodity instruments	We had the following net long positions as of: March 31, 2020 December 31, 2019 Units Notional Amounts Maximum Term (months) (a) Notional Amounts Maximum Term (months) (a) Natural gas futures purchased MMBtus 920,000 9 1,450,000 12 Natural gas options purchased, net MMBtus — 0 3,240,000 3 Natural gas basis swaps purchased MMBtus 790,000 9 1,290,000 12 Natural gas over-the-counter swaps, net (b) MMBtus 4,620,000 26 4,600,000 24 Natural gas physical contracts, net (c) MMBtus 1,104,725 12 13,548,235 12 Electric wholesale contracts (c) MWh 195,825 9 — 0 __________ (a) Term reflects the maximum forward period hedged. (b) As of March 31, 2020 , 800,000 MMBtus of natural gas over-the-counter swaps purchases were designated as cash flow hedges. (c) Volumes exclude contracts that qualify for the normal purchases and normal sales exception.
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table presents the fair value and balance sheet classification of our derivative instruments (in thousands) as of: Balance Sheet Location March 31, 2020 December 31, 2019 Derivatives designated as hedges: Asset derivative instruments: Current commodity derivatives Derivative assets, current $ 8 $ 1 Noncurrent commodity derivatives Other assets, non-current — 3 Liability derivative instruments: Current commodity derivatives Derivative liabilities, current (284 ) (490 ) Noncurrent commodity derivatives Other deferred credits and other liabilities (10 ) (29 ) Total derivatives designated as hedges $ (286 ) $ (515 ) Derivatives not designated as hedges: Asset derivative instruments: Current commodity derivatives Derivative assets, current $ 1,772 $ 341 Noncurrent commodity derivatives Other assets, non-current 156 2 Liability derivative instruments: Current commodity derivatives Derivative liabilities, current (568 ) (1,764 ) Noncurrent commodity derivatives Other deferred credits and other liabilities (28 ) (63 ) Total derivatives not designated as hedges $ 1,332 $ (1,484 )
Derivative Instruments, Gain (Loss)	The impacts of cash flow hedges on our Condensed Consolidated Statements of Comprehensive Income and Condensed Consolidated Statements of Income are presented below for the three months ended March 31, 2020 and 2019 . Note that this presentation does not reflect gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended March 31, Three Months Ended March 31, 2020 2019 2020 2019 Derivatives in Cash Flow Hedging Relationships Amount of (Gain)/Loss Recognized in OCI Income Statement Location Amount of Gain/(Loss) Reclassified from AOCI into Income (in thousands) (in thousands) Interest rate swaps $ 713 $ 713 Interest expense $ (713 ) $ (713 ) Commodity derivatives 257 (320 ) Fuel, purchased power and cost of natural gas sold (486 ) 554 Total $ 970 $ 393 $ (1,199 ) $ (159 ) Based on March 31, 2020 prices, a $0.3 million gain would be realized, reported in pre-tax earnings and reclassified from AOCI during the next 12 months. As market prices fluctuate, estimated and actual realized gains or losses will change during future periods. Derivatives Not Designated as Hedges The following table summarizes the impacts of derivative instruments not designated as hedge instruments on our Condensed Consolidated Statements of Income for the three months ended March 31, 2020 and 2019 . Note that this presentation does not reflect gains or losses arising from the underlying physical transactions; therefore, it is not indicative of the economic profit or loss we realized when the underlying physical and financial transactions were settled. Three Months Ended March 31, 2020 2019 Derivatives Not Designated as Hedging Instruments Income Statement Location Amount of Gain/(Loss) on Derivatives Recognized in Income (in thousands) Commodity derivatives - Electric Fuel, purchased power and cost of natural gas sold $ 1,362 $ — Commodity derivatives - Natural Gas Fuel, purchased power and cost of natural gas sold 766 25 $ 2,128 $ 25

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value Hierarchy, Measured on Recurring Basis	Recurring Fair Value Measurements Derivatives The commodity contracts for our Utilities segments are valued using the market approach and include forward strip pricing at liquid delivery points, exchange-traded futures, options, basis swaps and over-the-counter swaps and options (Level 2) for wholesale electric energy and natural gas contracts. For exchange-traded futures, options and basis swap assets and liabilities, fair value was derived using broker quotes validated by the exchange settlement pricing for the applicable contract. For over-the-counter instruments, the fair value is obtained by utilizing a nationally recognized service that obtains observable inputs to compute the fair value, which we validate by comparing our valuation with the counterparty. The fair value of these swaps includes a CVA based on the credit spreads of the counterparties when we are in an unrealized gain position or on our own credit spread when we are in an unrealized loss position. For additional information, see Note 1 to the Consolidated Financial Statements included in our 2019 Annual Report on Form 10-K filed with the SEC. As of March 31, 2020 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Gas Utilities $ — $ 1,949 $ — $ (13 ) $ 1,936 Commodity derivatives — Electric Utilities — 1,362 — — 1,362 Total $ — $ 3,311 $ — $ (13 ) $ 3,298 Liabilities: Commodity derivatives — Gas Utilities $ — $ 2,464 $ — $ (1,573 ) $ 891 Total $ — $ 2,464 $ — $ (1,573 ) $ 891 As of December 31, 2019 Level 1 Level 2 Level 3 Cash Collateral and Counterparty Netting Total (in thousands) Assets: Commodity derivatives — Gas Utilities $ — $ 1,433 $ — $ (1,085 ) $ 348 Total $ — $ 1,433 $ — $ (1,085 ) $ 348 Liabilities: Commodity derivatives — Gas Utilities $ — $ 5,254 $ — $ (2,909 ) $ 2,345 Total $ — $ 5,254 $ — $ (2,909 ) $ 2,345
Fair Value, by Balance Sheet Grouping	The following table presents the carrying amounts and fair values of financial instruments not recorded at fair value on the Condensed Consolidated Balance Sheets (in thousands) as of: March 31, 2020 December 31, 2019 Carrying Amount Fair Value Carrying Amount Fair Value Long-term debt, including current maturities (a) $ 3,142,630 $ 3,320,562 $ 3,145,839 $ 3,479,367 __________ (a) Long-term debt is valued based on observable inputs available either directly or indirectly for similar liabilities in active markets and therefore is classified as Level 2 in the fair value hierarchy. Carrying amount of long-term debt is net of deferred financing costs.

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Reclassification Out of Accumulated Other Comprehensive Income (Loss)	The following table details reclassifications out of AOCI and into net income. The amounts in parentheses below indicate decreases to net income in the Condensed Consolidated Statements of Income for the period (in thousands): Location on the Condensed Consolidated Statements of Income Amount Reclassified from AOCI Three Months Ended March 31, 2020 2019 Gains and (losses) on cash flow hedges: Interest rate swaps Interest expense $ (713 ) $ (713 ) Commodity contracts Fuel, purchased power and cost of natural gas sold (486 ) 554 (1,199 ) (159 ) Income tax Income tax benefit (expense) 285 35 Total reclassification adjustments related to cash flow hedges, net of tax $ (914 ) $ (124 ) Amortization of components of defined benefit plans: Prior service cost Operations and maintenance $ 30 $ 19 Actuarial gain (loss) Operations and maintenance (597 ) (220 ) (567 ) (201 ) Income tax Income tax benefit (expense) 88 48 Total reclassification adjustments related to defined benefit plans, net of tax $ (479 ) $ (153 ) Total reclassifications $ (1,393 ) $ (277 )
Schedule of Accumulated Other Comprehensive Income (Loss)	Balances by classification included within AOCI, net of tax on the accompanying Condensed Consolidated Balance Sheets were as follows (in thousands): Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total As of December 31, 2019 $ (15,122 ) $ (456 ) $ (15,077 ) $ (30,655 ) Other comprehensive income (loss) before reclassifications — (175 ) 55 (120 ) Amounts reclassified from AOCI 543 371 479 1,393 As of March 31, 2020 $ (14,579 ) $ (260 ) $ (14,543 ) $ (29,382 ) Interest Rate Swaps Commodity Derivatives Employee Benefit Plans Total As of December 31, 2018 $ (17,307 ) $ 328 $ (9,937 ) $ (26,916 ) Other comprehensive income (loss) before reclassifications — 180 — 180 Amounts reclassified from AOCI 550 (426 ) 153 277 As of March 31, 2019 $ (16,757 ) $ 82 $ (9,784 ) $ (26,459 )

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2020
Defined Benefit Plan [Abstract]
Schedule of Net Benefit Costs	The components of net periodic benefit cost for the Defined Benefit Pension Plan were as follows (in thousands): Three Months Ended March 31, 2020 2019 Service cost $ 1,353 $ 1,346 Interest cost 3,357 4,343 Expected return on plan assets (5,648 ) (6,100 ) Prior service cost (benefit) — 6 Net loss (gain) 2,093 941 Net periodic benefit cost $ 1,155 $ 536 Defined Benefit Postretirement Healthcare Plan The components of net periodic benefit cost for the Defined Benefit Postretirement Healthcare Plan were as follows (in thousands): Three Months Ended March 31, 2020 2019 Service cost $ 514 $ 454 Interest cost 412 560 Expected return on plan assets (45 ) (57 ) Prior service cost (benefit) (137 ) (99 ) Net loss (gain) 5 — Net periodic benefit cost $ 749 $ 858 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans The components of net periodic benefit cost for the Supplemental Non-qualified Defined Benefit and Defined Contribution Plans were as follows (in thousands): Three Months Ended March 31, 2020 2019 Service cost $ (1,370 ) $ 1,285 Interest cost 275 324 Net loss (gain) 426 134 Net periodic benefit cost $ (669 ) $ 1,743
Schedule of Defined Benefit Plans Contributions	Contributions made in the first quarter of 2020 and anticipated contributions for 2020 and 2021 are as follows (in thousands): Contributions Made Additional Contributions Contributions Three Months Ended March 31, 2020 Anticipated for 2020 Anticipated for 2021 Defined Benefit Pension Plan $ — $ 12,700 $ 12,700 Non-pension Defined Benefit Postretirement Healthcare Plans $ 1,335 $ 4,006 $ 5,364 Supplemental Non-qualified Defined Benefit and Defined Contribution Plans $ 355 $ 1,065 $ 1,614

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2020
Investments, All Other Investments [Abstract]
Investments	The following table presents the carrying value of our investments (in thousands) as of: March 31, 2020 December 31, 2019 Investment in privately held oil and gas company $ 1,500 $ 8,359 Cash surrender value of life insurance contracts 13,235 13,056 Other investments 515 514 Total investments $ 15,250 $ 21,929

Management's Statement_ Managem

Management's Statement: Management Statement (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (207)	$ 3,390
Accounting Standards Update 2016-13
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (200)

Management's Statement_ Reclass

Management's Statement: Reclassification (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fuel, purchased power and cost of natural gas sold	$ 187,879	$ 249,742
Operations and maintenance	125,466	123,584
Taxes - property and production	$ 14,118	13,325
Scenario, Adjustment [Member]
Fuel, purchased power and cost of natural gas sold		900
Operations and maintenance		(300)
Taxes - property and production		(300)
Other Cost and Expense, Operating		$ (400)

Disaggregation of Revenue (Deta

Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 530,209	$ 597,970
Total revenues	537,050	597,810
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,564	7,701
Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	523,645	590,269
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	6,841	(160)
Retail - Electric , Natural Gas and Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	453,451	515,439
Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	43,969	44,085
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7,407	10,599
Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,366	4,685
Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23,016	23,162
Inter-company Revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(38,642)	(36,878)
Total revenues	(39,033)	(37,871)
Inter-company Revenues | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(7,839)	(8,128)
Inter-company Revenues | Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(30,803)	(28,750)
Inter-company Revenues | Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	(391)	(993)
Inter-company Revenues | Retail - Electric , Natural Gas and Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(7,839)	(8,128)
Inter-company Revenues | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(139)	(432)
Inter-company Revenues | Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(23,612)	(21,891)
Inter-company Revenues | Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(2,639)	(2,224)
Inter-company Revenues | Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(4,413)	(4,203)
Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	173,916	182,673
Total revenues	174,139	182,927
Electric Utilities | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Electric Utilities | Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	173,916	182,673
Electric Utilities | Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	223	254
Electric Utilities | Retail - Electric , Natural Gas and Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	148,640	153,463
Electric Utilities | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Electric Utilities | Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,552	8,343
Electric Utilities | Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4,867	6,692
Electric Utilities | Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,857	14,175
Gas Utilities
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	355,065	412,199
Total revenues	360,773	411,080
Gas Utilities | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Gas Utilities | Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	355,065	412,199
Gas Utilities | Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	5,708	(1,119)
Gas Utilities | Retail - Electric , Natural Gas and Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	298,247	354,275
Gas Utilities | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44,108	44,517
Gas Utilities | Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Gas Utilities | Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	138	217
Gas Utilities | Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12,572	13,190
Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	25,467	24,147
Total revenues	25,966	25,245
Power Generation | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Power Generation | Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	25,467	24,147
Power Generation | Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	499	1,098
Power Generation | Retail - Electric , Natural Gas and Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Power Generation | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Power Generation | Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	25,467	24,147
Power Generation | Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Power Generation | Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Mining
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,403	15,829
Total revenues	15,205	16,429
Mining | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,403	15,829
Mining | Services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Mining | Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	802	600
Mining | Retail - Electric , Natural Gas and Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,403	15,829
Mining | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Mining | Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Mining | Market - off-system sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Mining | Transmission/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0

Business Segment Information_ I

Business Segment Information: Information Relating to Segment Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019
Segment Reporting Information
Revenue from contracts with customers	$ 530,209		$ 597,970
Revenues	537,050		597,810
Operating income	153,185		160,131
Interest expense, net	(35,453)		(34,717)
Impairment of investment	(6,859)	$ (20,000)	0
Other Nonoperating Income (Expense) Including Allowance For Funds Used During Construction, Equity	2,353		(789)
Income tax (expense)	(16,002)		(17,263)
Net income	97,224		107,362
Net income attributable to noncontrolling interest	(4,050)		(3,554)
Net income available for common stock	93,174		103,808
Inter-company Revenues
Segment Reporting Information
Revenue from contracts with customers	(38,642)		(36,878)
Revenues	(39,033)		(37,871)
Consolidation, Eliminations
Segment Reporting Information
Revenue from contracts with customers	0		0
Corporate
Segment Reporting Information
Operating income	160		(507)
Electric Utilities
Segment Reporting Information
Revenue from contracts with customers	173,916		182,673
Revenues	174,139		182,927
Operating income	35,650		41,020
Gas Utilities
Segment Reporting Information
Revenue from contracts with customers	355,065		412,199
Revenues	360,773		411,080
Operating income	102,897		103,314
Power Generation
Segment Reporting Information
Revenue from contracts with customers	25,467		24,147
Revenues	25,966		25,245
Operating income	11,349		11,967
Mining
Segment Reporting Information
Revenue from contracts with customers	14,403		15,829
Revenues	15,205		16,429
Operating income	3,129		4,337
Other Revenues
Segment Reporting Information
Revenues	6,841		(160)
Other Revenues | Inter-company Revenues
Segment Reporting Information
Revenues	(391)		(993)
Other Revenues | Consolidation, Eliminations
Segment Reporting Information
Revenues	0		0
Other Revenues | Electric Utilities
Segment Reporting Information
Revenues	223		254
Other Revenues | Gas Utilities
Segment Reporting Information
Revenues	5,708		(1,119)
Other Revenues | Power Generation
Segment Reporting Information
Revenues	499		1,098
Other Revenues | Mining
Segment Reporting Information
Revenues	802		600
External Operating Revenue
Segment Reporting Information
Revenue from contracts with customers	530,209		597,970
External Operating Revenue | Electric Utilities
Segment Reporting Information
Revenue from contracts with customers	167,503		176,663
External Operating Revenue | Gas Utilities
Segment Reporting Information
Revenue from contracts with customers	354,287		411,500
External Operating Revenue | Power Generation
Segment Reporting Information
Revenue from contracts with customers	1,855		2,257
External Operating Revenue | Mining
Segment Reporting Information
Revenue from contracts with customers	6,564		7,550
External Operating Revenue | Other Revenues
Segment Reporting Information
Revenues	6,841		(160)
External Operating Revenue | Other Revenues | Electric Utilities
Segment Reporting Information
Revenues	223		254
External Operating Revenue | Other Revenues | Gas Utilities
Segment Reporting Information
Revenues	5,708		(1,119)
External Operating Revenue | Other Revenues | Power Generation
Segment Reporting Information
Revenues	443		436
External Operating Revenue | Other Revenues | Mining
Segment Reporting Information
Revenues	467		269
Inter-company Operating Revenue | Electric Utilities
Segment Reporting Information
Revenue from contracts with customers	6,413		6,010
Inter-company Operating Revenue | Gas Utilities
Segment Reporting Information
Revenue from contracts with customers	778		699
Inter-company Operating Revenue | Power Generation
Segment Reporting Information
Revenue from contracts with customers	23,612		21,890
Inter-company Operating Revenue | Mining
Segment Reporting Information
Revenue from contracts with customers	7,839		8,279
Inter-company Operating Revenue | Other Revenues | Electric Utilities
Segment Reporting Information
Revenues	0		0
Inter-company Operating Revenue | Other Revenues | Gas Utilities
Segment Reporting Information
Revenues	0		0
Inter-company Operating Revenue | Other Revenues | Power Generation
Segment Reporting Information
Revenues	56		662
Inter-company Operating Revenue | Other Revenues | Mining
Segment Reporting Information
Revenues	$ 335		$ 331

Business Segment Information_ S

Business Segment Information: Segment and Corporate Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 7,648,814	$ 7,558,457
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	180,512	130,245
Electric Utilities
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,931,902	2,900,983
Gas Utilities
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,043,539	4,032,339
Power Generation
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	412,572	417,715
Mining
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 80,289	$ 77,175

Selected Balance Sheet Inform_3

Selected Balance Sheet Information: Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Selected Balance Sheet Information [Abstract]
Accounts receivable, trade	$ 162,138	$ 144,747
Unbilled revenue	81,927	113,502
Less: Allowance for doubtful accounts	(5,162)	(2,444)
Accounts receivable, net	$ 238,903	$ 255,805

Selected Balance Sheet Inform_4

Selected Balance Sheet Information: Materials and Supplies (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Selected Balance Sheet Information [Abstract]
Materials and supplies	$ 88,346	$ 82,809
Fuel - Electric Utilities	3,049	2,425
Natural gas in storage	1,499	31,938
Total materials, supplies and fuel	$ 92,894	$ 117,172

Selected Balance Sheet Inform_5

Selected Balance Sheet Information: Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Selected Balance Sheet Information [Abstract]
Accrued employee compensation, benefits and withholdings	$ 45,070	$ 62,837
Accrued property taxes	45,666	44,547
Customer deposits and prepayments	43,524	54,728
Accrued interest	43,776	31,868
Other (none of which is individually significant)	25,409	32,787
Total accrued liabilities	$ 203,445	$ 226,767

Regulatory Matters (Details)

Regulatory Matters (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Regulatory assets
Regulatory assets	$ 272,229	$ 271,344
Less current regulatory assets	(49,415)	(43,282)
Regulatory assets, non-current	222,814	228,062
Regulatory liabilities
Regulatory liabilities	558,494	536,652
Less current regulatory liabilities	(54,345)	(33,507)
Regulatory liabilities, non-current	504,149	503,145
Deferred energy and gas costs
Regulatory liabilities
Regulatory liabilities	40,002	17,278
Employee benefit plans
Regulatory liabilities
Regulatory liabilities	41,518	43,349
Cost of removal
Regulatory liabilities
Regulatory liabilities	170,954	166,727
Excess deferred income taxes
Regulatory liabilities
Regulatory liabilities	283,690	285,438
TCJA revenue reduction
Regulatory liabilities
Regulatory liabilities	5,147	3,418
Other regulatory liabilities
Regulatory liabilities
Regulatory liabilities	17,183	20,442
Deferred energy and gas costs
Regulatory assets
Regulatory assets	35,687	34,088
Deferred gas cost adjustments
Regulatory assets
Regulatory assets	0	1,540
Gas price derivatives
Regulatory assets
Regulatory assets	1,302	3,328
Deferred taxes on AFUDC
Regulatory assets
Regulatory assets	7,739	7,790
Employee benefit plans
Regulatory assets
Regulatory assets	117,150	115,900
Environmental
Regulatory assets
Regulatory assets	1,439	1,454
Loss on reacquired debt
Regulatory assets
Regulatory assets	24,299	24,777
Renewable energy standard adjustment
Regulatory assets
Regulatory assets	340	1,622
Deferred taxes on flow through accounting
Regulatory assets
Regulatory assets	44,589	41,220
Decommissioning costs
Regulatory assets
Regulatory assets	10,248	10,670
Gas supply contract termination
Regulatory assets
Regulatory assets	7,007	8,485
Other regulatory assets
Regulatory assets
Regulatory assets	$ 22,429	$ 20,470

Regulatory Matters_ Rate Review

Regulatory Matters: Rate Review (Details) $ in Millions	Apr. 14, 2020	Aug. 02, 2019MW	Feb. 01, 2019USD ($)utility
Federal Energy Regulatory Commission (FERC) | Black Hills Wyoming and Wyoming Electric
Public Utilities, General Disclosures [Line Items]
Pending FERC Approval - Number of Megawatts Capacity to be Purchased and Delivered Through Intercompany Agreement | MW		60
Unrecorded Unconditional Purchase Obligation, Term		20 years
Colorado Public Utilities Commission (CPUC) | Black Hills Energy, Colorado Gas | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	9.20%
Rate Review Filed with the Regulatory Agency | Colorado Public Utilities Commission (CPUC) | Black Hills Energy, Colorado Gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Number of Gas Distribution Territories Consolidating | utility			2
Public Utilities, Requested Rate Increase (Decrease), Amount | $			$ 2.5
Public Utilities, Requested Equity Capital Structure, Percentage			9.50%

Earnings Per Share_ Earnings Pe

Earnings Per Share: Earnings Per Share Reconciliation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income available for common stock	$ 93,174	$ 103,808
Weighted average shares - basic (in shares)	61,778	59,920
Dilutive effect of:
Equity compensation (in shares)	78	140
Weighted average shares - diluted (in shares)	61,856	60,060
Earnings (loss) per share, Basic (usd per share)	$ 1.51	$ 1.73
Earnings (loss) per share, Diluted (usd per share)	$ 1.51	$ 1.73

Earnings Per Share_ Anti-diluti

Earnings Per Share: Anti-dilutive shares (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares (in shares)	38	6
Equity compensation - (in shares)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares (in shares)	12	6
Restricted Stock (in shares)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares (in shares)	26	0

Notes Payable, Current Maturi_3

Notes Payable, Current Maturities and Debt: Schedule of Short-term Debt and Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Short-term Debt [Line Items]
Notes payable	$ 319,125		$ 349,500
Letters of Credit	17,281		30,274
Net (payments) borrowings of short-term debt	(30,375)	$ (20,970)
Commercial Paper
Short-term Debt [Line Items]
Notes payable	$ 154,125		349,500
Short-term interest rate	1.74%
Revolving Credit Facility
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 750,000
Notes payable	165,000		0
Letters of Credit	$ 17,281		$ 30,274
Short-term interest rate	1.92%

Notes Payable, Current Maturi_4

Notes Payable, Current Maturities and Debt: Debt Covenants (Details)	Mar. 31, 2020
Line of Credit Facility [Line Items]
Ratio of Indebtedness to Net Capital	0.582
Maximum
Line of Credit Facility [Line Items]
Consolidated Indebtedness to Capitalization Ratio	0.65

Notes Payable, Current Maturi_5

Notes Payable, Current Maturities and Debt: Long-Term Debt (Details) $ in Millions	Mar. 24, 2020USD ($)
Electric Utilities | South Dakota Electric | Bonds Due 2024
Extinguishment of Debt, Amount	$ 2.9

Equity_ Equity Issuance (Detail

Equity: Equity Issuance (Details) - Private Placement $ / shares in Units, shares in Millions, $ in Millions	Feb. 27, 2020USD ($)$ / sharesshares
Sale of Stock, Number of Shares Issued in Transaction | shares	1.2
Sale of Stock, Price Per Share | $ / shares	$ 81.77
Sale of Stock, Consideration Received on Transaction	$ 99
Payments of Stock Issuance Costs	$ 1

Equity_ At-the-Market Equity Of

Equity: At-the-Market Equity Offering Program (Details) - USD ($) $ in Millions	Aug. 04, 2017	Mar. 31, 2019
At The Market Equity Offering Program Authorized Aggregate Value	$ 300
Common Stock
At The Market Equity Program Proceeds from Sale of Stock		$ 20
At The Market Equity Offering Program Shares Issued		300,000
Payments of Stock Issuance Costs		$ 0.2

Risk Management and Derivativ_3

Risk Management and Derivatives: Utilities (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)MMBTUmW	Dec. 31, 2019MMBTUmW
Natural Gas, Distribution | Cash Flow Hedging
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	800,000
Natural Gas, Distribution | Natural gas futures purchased
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	920,000	1,450,000
Derivative, Remaining Maturity	9 months	12 months
Natural Gas, Distribution | Natural gas options purchased, net
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	0	3,240,000
Derivative, Remaining Maturity	0 months	3 months
Natural Gas, Distribution | Natural gas basis swaps purchased
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	790,000	1,290,000
Derivative, Remaining Maturity	9 months	12 months
Natural Gas, Distribution | Natural gas over-the-counter swaps, net
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	4,620,000	4,600,000
Derivative, Remaining Maturity	26 months	24 months
Credit Risk Derivative Liabilities, at Fair Value | $	$ 0.5
Natural Gas, Distribution | Natural gas physical contracts, net
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	1,104,725	13,548,235
Derivative, Remaining Maturity	12 months	12 months
Electricity | Electric wholesale contracts
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | mW	195,825	0
Derivative, Remaining Maturity	9 months	0 months

Risk Management and Derivativ_4

Risk Management and Derivatives: Derivatives by Balance Sheet Classification (Details) - Commodity Contract - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair Value Hedges, Net	$ (286)	$ (515)
Designated as Hedging Instrument | Derivative assets — current
Derivatives, Fair Value [Line Items]
Fair Value Hedge Assets	8	1
Designated as Hedging Instrument | Other assets, non-current
Derivatives, Fair Value [Line Items]
Fair Value Hedge Assets	0	3
Designated as Hedging Instrument | Derivative liabilities — current
Derivatives, Fair Value [Line Items]
Fair Value Hedge Liabilities	(284)	(490)
Designated as Hedging Instrument | Other deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Fair Value Hedge Liabilities	(10)	(29)
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair Value Hedges, Net	1,332	(1,484)
Not Designated as Hedging Instrument | Derivative assets — current
Derivatives, Fair Value [Line Items]
Fair Value Hedge Assets	1,772	341
Not Designated as Hedging Instrument | Other assets, non-current
Derivatives, Fair Value [Line Items]
Fair Value Hedge Assets	156	2
Not Designated as Hedging Instrument | Derivative liabilities — current
Derivatives, Fair Value [Line Items]
Fair Value Hedge Liabilities	(568)	(1,764)
Not Designated as Hedging Instrument | Other deferred credits and other liabilities
Derivatives, Fair Value [Line Items]
Fair Value Hedge Liabilities	$ (28)	$ (63)

Risk Management and Derivativ_5

Risk Management and Derivatives: Derivatives Designated as Hedges (Details) - Cash Flow Hedging - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (1,199)	$ (159)
Designated as Hedging Instrument
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	970	393
Natural Gas, Distribution
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	300
Interest rate swaps | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	713	713
Commodity Contract | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	257	(320)
Interest expense incurred net of amounts capitalized (including amortization of debt issuance costs, premiums and discounts) | Interest rate swaps
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(713)	(713)
Cost of Sales | Commodity Contract
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (486)	$ 554

Risk Management and Derivativ_6

Risk Management and Derivatives: Derivatives Not Designated as Hedge Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative [Line Items]
Regulatory assets	$ 272,229		$ 271,344
Gas price derivatives
Derivative [Line Items]
Regulatory assets	1,302		$ 3,328
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	2,128	$ 25
Not Designated as Hedging Instrument | Cost of Sales | Electricity
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	1,362	0
Not Designated as Hedging Instrument | Cost of Sales | Natural Gas, Distribution
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 766	$ 25

Fair Value Measurements_ Schedu

Fair Value Measurements: Schedule of Fair Values (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	$ (13)	$ (1,085)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(1,573)	(2,909)
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Total	3,298	348
Derivative Liabilities, Total	891	2,345
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Total	0	0
Derivative Liabilities, Total	0	0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Total	3,311	1,433
Derivative Liabilities, Total	2,464	5,254
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Total	0	0
Derivative Liabilities, Total	0	0
Gas Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(13)	(1,085)
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(1,573)	(2,909)
Gas Utilities | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	1,936	348
Derivative Liabilities, Fair Value Disclosure	891	2,345
Gas Utilities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0
Derivative Liabilities, Fair Value Disclosure	0	0
Gas Utilities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	1,949	1,433
Derivative Liabilities, Fair Value Disclosure	2,464	5,254
Gas Utilities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0	0
Derivative Liabilities, Fair Value Disclosure	0	$ 0
Electric Utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	0
Electric Utilities | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	1,362
Electric Utilities | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	0
Electric Utilities | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	1,362
Electric Utilities | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets, Commodity Derivatives	$ 0

Fair Value Measurements_ Other

Fair Value Measurements: Other Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 3,142,630	$ 3,145,839
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 3,320,562	$ 3,479,367

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss): Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Condensed Statement of Income Captions [Line Items]
Interest Expense	$ 35,781	$ 35,016
Fuel, purchased power and cost of natural gas sold	187,879	249,742
Operations and maintenance	125,466	123,584
Income before Income Taxes	113,226	124,625
Income tax benefit (expense)	(16,002)	(17,263)
Net income (loss)	97,224	107,362
Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Net income (loss)	(1,393)	(277)
Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Income before Income Taxes	(1,199)	(159)
Income tax benefit (expense)	285	35
Net income (loss)	(914)	(124)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost | Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Operations and maintenance	30	19
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Operations and maintenance	(597)	(220)
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Income before Income Taxes	(567)	(201)
Income tax benefit (expense)	88	48
Net income (loss)	(479)	(153)
Interest rate swaps | Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Interest Expense	(713)	(713)
Commodity Contract | Cash Flow Hedging | Reclassification out of Accumulated Other Comprehensive Income
Condensed Statement of Income Captions [Line Items]
Fuel, purchased power and cost of natural gas sold	$ (486)	$ 554

Other Comprehensive Income (L_4

Other Comprehensive Income (Loss): Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	$ (30,655)	$ (26,916)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(29,382)	(26,459)
Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(15,077)	(9,937)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	55	0
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(14,543)	(9,784)
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	479	153
Accumulated Other Comprehensive Income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(120)	180
Accumulated Other Comprehensive Income (loss) | Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1,393	277
Interest Rate Swaps | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(15,122)	(17,307)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(14,579)	(16,757)
Interest Rate Swaps | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	543	550
Commodity Contract | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period Start	(456)	328
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(175)	180
Accumulated Other Comprehensive Income (Loss), Net of Tax, Period End	(260)	82
Commodity Contract | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 371	$ (426)

Employee Benefit Plans_ Change

Employee Benefit Plans: Change in Accounting Principle (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Accounting Principle, Effect of Change on Net Income	$ 0.4
Decrease in Prior Service Costs
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Accounting Principle, Effect of Adoption	0.6
increase in Income Tax Expense
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Accounting Principle, Effect of Adoption	$ 0.2

Employee Benefit Plans_ Funding

Employee Benefit Plans: Funding Status of Employee Benefit Plans (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Benefit plan liabilities	$ 152,693	$ 154,472
Pension Plan
Benefit plan liabilities	$ 46,000	$ 51,000

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 1,353	$ 1,346
Interest cost	3,357	4,343
Expected return on plan assets	(5,648)	(6,100)
Prior service cost (benefit)	0	6
Net loss (gain)	2,093	941
Net periodic benefit cost	1,155	536
Payment for Pension and Other Postretirement Benefits [Abstract]
Contributions by Employer	0
Estimated Future Employer Contributions in Current Fiscal Year	12,700
Estimated Future Employer Contributions in Next Fiscal Year	12,700
Other Postretirement Benefits Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	514	454
Interest cost	412	560
Expected return on plan assets	(45)	(57)
Prior service cost (benefit)	(137)	(99)
Net loss (gain)	5	0
Net periodic benefit cost	749	858
Payment for Pension and Other Postretirement Benefits [Abstract]
Contributions by Employer	1,335
Estimated Future Employer Contributions in Current Fiscal Year	4,006
Estimated Future Employer Contributions in Next Fiscal Year	5,364
Supplemental Non-qualified Defined Benefit and Defined Contribution Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	(1,370)	1,285
Interest cost	275	324
Net loss (gain)	426	134
Net periodic benefit cost	(669)	$ 1,743
Payment for Pension and Other Postretirement Benefits [Abstract]
Contributions by Employer	355
Estimated Future Employer Contributions in Current Fiscal Year	1,065
Estimated Future Employer Contributions in Next Fiscal Year	$ 1,614

Commitments and Contingencies_

Commitments and Contingencies: Future Purchase Agreement - Related Party (Details)	Aug. 02, 2019MW
Black Hills Wyoming and Wyoming Electric | Federal Energy Regulatory Commission (FERC)
Unrecorded Unconditional Purchase Obligation [Line Items]
Pending FERC Approval - Number of Megawatts Capacity to be Purchased and Delivered Through Intercompany Agreement	60

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income tax benefit (expense)	$ (16,002)	$ (17,263)
Effective Tax Rate	14.10%	13.90%

Investments (Details)

Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Feb. 28, 2019
Assets used to Acquire Other Investments					$ 28,000
Impairment of investment	$ 6,859	$ 20,000	$ 0
Investments	15,250			$ 21,929
Equity Securities
Investments	1,500			8,359
Cash surrender value of life insurance contracts
Investments	13,235			13,056
Total investments
Investments	$ 515			$ 514
Valuation, Income Approach
Discount Rate Used in Valuation of Fair Value of Oil and Gas Reserve Quantities		10.00%